Signaling system



April 14, 1931.

w. 1.. EDISON 1,800,821

SIGNALING SYSTEM- Filed June 27, 1928 er [1 mm 44%; 4; min

Patented Apr. 14, 1931 UNITED STATES PATENT OFFICE WILLIAM LESLIE EDISON, OF WILMINGTON, DELAWARE, ASSIGNOR TO THE W. L.

EDISON MANUFACTURING CORPORATION, OF WILMINGTON, DELAWARE, A COR- PORATION OF DELAWARE SIGNALING SYSTEM Application filed June 27,

This invention relates to a high frequency alternating current system and more particularly to means for interconnecting the successive tubes of an amplifying sy-stem. The

6 system herein disclosed is particularly adapted to the amplification of radio signals.

At present the high frequency radio signals are amplified by a succession of thermionic tubes which are successively coupled in one of three Ways the coupling device con sisting either of a step-up transformer, re-

sistance coupling or an impedance coupling,

the output of the plate of one tube being hereby caused to impress a variation of volt- 5 age on the grid of a succeeding tube, whereby the plate current of such suceeding tube is proportionately varied.

After the signals are amplified to a sufficient degree, they are rectified by means of a detector. The audio frequency signals subsequently produced are further amplified through a succession of tubes coupled. in a similar manner.

The disadvantages (if transformer coupling, particularly between the tubes in which audio amplification is accomplished, are the space required and the cost, since the transformers suitable for audio frequency require a large amount of copper winding and a large iron core, if faithful reproduction of the radio signal is to be obtained. In case it is desirable to use more than two transformer coupled stages, it is necessary that the third and fourth stages be carefully by-passed by condensers, and that the trans formers be shielded and the shields grounded to prevent interaction between the stages with resultant feed-back, audio frequency oscillations and howling.

The resistance coupling is characterized by a low amplification factor, which is practically represented by the tube gain only. Accordingly, for a given amplification it is necessary to use a larger number of stages and tubes than are necessary when using transformer coupling. Large losses in the coupling resistances then occur and high B voltage is necessary. A further disadvantage of this method is the tendency of this type of coupling to set up audio frequency osci1la- 1928. Serial No. 288,563.

tions when fed by a B battery eliminator, due to inter-tube coupling through the voltage supply device, requiring extensive lay-passing of the voltage supply by condensers for their elimination. The disadvantage of the impedance or reactance coupling is low amplification factor and high cost, since three stages of such coupling are necessary to accomplish the work of two transformer coupled stages. For faithful reproduction of the radio signal, large and expensive iinpedances and large condensers are required.

The object of the present invention is to provide an intertube coupling from which the above disadvantages are eliminated, the simplicity of the apparatus improved, and the quality of the reproduction rendered far su perior to that heretofore obtained. A further object is the provision in an alternating or pulsating direct current circuit of a device which produces effects of peculiar character which will be described hereafter.

In the drawing:

1 is a diagrammatic illustration of a portion of a circuit embodying the improved amplifying system.

Fig. 2 is a sectional view showing a cell which is used in connection with the system shown in Fig. 1.

At V and V are shown thermionic tubes which may be of any suitable type commonly used in the amplification of high frequency or audio frequency signals. As disclosed, these tubes are triodes, each of which is provided with an electron emissive cathode (illustrated as a filament), a grid and a plate.

t will. be understood, of course, that a quadrode might be used in a manner which will be obvious. By a suitable variation of the various elements disclosed in the circuit, it will be clear that either high radio frequency signals or relatively low audio frequency signals may be amplified. Accordingly, Fig. 1 may be taken to illustrate either successive radio or audio amplification stages. The input into tube V is impressed as a voltage between the grid and cathode. As a result, a variation is made in the plate circuit. This plate circuit includes a coupling resistance R and a source of B Voltage conventionally shown as a battery B The resistance R may correspond to the ordinary couphng resistance used in resistance coupled amplification stages and may, for example, have a resistance of approximately ten thousand ohms. In the ordinary resistance coupling, the end of this resistance R opposite that connected to the source of B voltage. would be connected directly to the plate. The grid of the successive tubeV would then be con or to a further stage of amplificationor to a loud speakeror phones. The source of B voltage for tube V is indicated at B 7 Insteadoi the ordinary connections, cells X and X are interposed as illustrated in Fig. 1-. Each of these cells includes a vessel 2 which, as disclosed, is of insulating material and carries an insulating cap 4. Suitable metallic electrodes 6 extend downwardly through the insulating cap a into a liquid 8 and are provided at their tops with binding posts 10 for the connection of lead wires. The liquid 8, it is found, may be either an aqueous solution of an electrolyte, for. ex a1nple,a salt, acid or alkali, or it may be a non-electrolyte. such as distilled water, al.- cohol, light lubricating oil, glycerine, olive oil or the like. It is found that a dilute solution of ordinary salt gives the best results although other electrolytes give very good results, and fair results are obtained by the use of various non-electrolytes such as enum erated above. It will'be understoodthat the substance of the cell need not necessarily be a liquid but might, for example, he made semi-solid by means of a gelatinous substance, such as gelatin or silicic acid, although such semi-solid and gelatinous substances are slightly inferior to the liquids in action. It will, accordingly, be understood that the term liquid used in the claims is intended to cover such equivalent semi-solid material. Vl hile the cell has been shown as comprising a non-conducting cup, it will be obviousthat a metallic cup might be employed, thecup then forming one of the electrodes.

'As shown in Fig. 1, one of these cells, X

is connected into the conventional circuit by breaking the same open and connecting the three. electrodes respectively to the plate of the first tube, to coupling resistance R and to the blocking concenser C. The two electrodes of the second cell K are similarly connected to the blocking condenser C, and to over the old types in that tube noises are alosent and faithful reproduction is obtained, the intertube connecting device exercising no selectivity with respect to high or low notes, giving a true amplifica ion of all alike.

It will. be noted that no grid leak is used in the circuit shown. It has been heretofore considered necessary to use a grid leak to bypass a blocking condenser such as (l, but when connections are made as indicated in Fig. 1, cells X and X being used, no grid leak is necessary. If, however, cells X and are eliminated and connectionsmade as in the ordinary resistance coupled ampliher, it is found that the tube blocks, necessitating the use of a gridleak. In case it is desirable to use a grid leak because of peculiar tube characteristics, heavy load, or

the like, it may be connected to a third electrode in cell and to the filament of tube V The reason for the improved operation or appears however that the cells have some function which isnot clearly understood. As stated above, the circu t still functions even though relatively poor conducting liquids, such as those enumerated, are used in the: cells, these liquids usually being regarded as non-electrolytes. Since a great variety of liquids may apparently be used which have no properties which have heretofore been consideredto render them equivalent, it is not desired to limit'the claims to the use of any particular group of known liquids, since apparently the result is due 'to the substitution of almost any liquid or gelatinous substance partaking of liquid characteristics. I

It will be noted that the plate circuit of tube V includes'cell X impedance R (which may obviously be a resistance, in-

cathode of a succeeding tube and coupled with said plate circuit, the coupling means between said circults including a common portlon of h gh lmpedance, means for 1mparting a positive potential to the plate of the first tube relative to the cathode thereof, and a cell interposed in said circuits, said cell including a body of liquid and a plu rality of electrodes contacting with said liquid, one electrode being connected with the common portion of the circuits, another electrode being connected with the plate of the first tube, and a third electrode being connected with the grid of the second tube.

2. An amplifying system including a plurality of thermionic tubes, each of which has cathode, grid and plate elements, a plate circuit joining the plate and cathode of one tube, a grid circuit joining the grid and cathode of a succeeding tube and coupled with said plate circuit, the coupling means between said circuitsincluding a common portion of high impedance, means for imparting a positive potential to the plate of the first tube relative to the cathode thereof, a cell interposed in said circuits, said cell including a body of liquid and a plurality of electrodes contacting with said liquid, one electrode being connected with the common portion of the circuits, another electrode being connected with the plate of the first tube, and a third electrode being connected with the grid. of the second tube, a condenser interposed in said grid circuit between the grid and said cell, and a second cell interposed in the grid circuit between the condenser and grid, said second cell including a body of liquid and a plurality of electrodes contacting with said liquid.

3. An amplifying system including a plurality of thermionic tubes, each of which has cathode, grid and plate elements, a plate circuit joining the plate and cathode of one tube, a grid circuit joining the grid and cathode of a succeeding tube and coupled with said plate circuit, the coupling means between said circuits including a common portion of high impedance, means for imparting a positive potential to the plate of the first tube relative to the cathode thereof, a cell interposed in said circuits, said cell including a body of liquid and a plurality of electrodes contacting with said liquid, one electrode being connected with the common portion of the circuits, another electrode being connected with the plate of the first tube, and a third electrode being connected with the grid of the second tube, a condenser interposed in said grid circuit between the grid and said cell, and a second cell interposed in the grid circuit between the condenser and grid, said second cell including a body of liquid and a plurality of electrodes contacting with said liquid, one electrode being connected to said grid, a second electrode being connected to said condenser, and a third electrode being connected through a resistance to the filament of the second tube.

4. An amplifying system including a plurality of thermionic tubes, each of which has cathode, grid and plate elements, a plate circuit joining the plate and cathode of one tube, a grid circuit joining the grid and cathode of a succeeding tube and coupled with said plate circuit, the coupling means between said circuits including a common portion of high impedance, means for imparting a ositive potential to the plate of the first tulie relative to the cathode thereof, and a cell interposed in the common portion of said circuits, said cell including a body of liquid and a plurality of electrodes contactiug with said liquid.

5. An amplifying system including a plurality of thermionic tubes, each of which has cathode, grid and plate elements, a plate circuit joining the plate and cathode of one tube, a grid circuit joining the grid and cathode of a succeeding tube and coupled with said plate circuit, the coupling means between said circuits including a common portion of high impedance, means for imparting a positive potential to the plate of the first tube relative to the cathode thereof, a cell interposed in the common portion of said circuits, said cell including a body of liquid and a plurality of electrodes contacting with said liquid, and a condenser interposed in the grid circuit between the grid and the cell.

In testimony of which invention, I have hereunto set my hand, at Wilmington, Del., on this 21st day of June, 1928.

WILLIAM LESLIE EDISON. 

